Field of the Invention
The present invention relates to an improved system and method for manufacturing flexible laminated circuit boards. More particularly, the present invention provides an improved method for manufacturing flexible laminated printed circuit boards (PCBs) with manual and automated optical pinless and partial pinless bonded layup features that minimize alignment error in manufacturing.
Description of the Related Art
The related art involves a process for producing rigid printed electronic circuits, including multilayer circuits by endothermic induction heading as discussed in PCT/IT2003/000403 by Ceraso, et al., (published as WO 2004/103042) [the Ceraso system] the entire contents of which are herein incorporated by reference. During processing, a ferromagnetic core having an alternating current winding is positioned proximate the endothermic heating pile and induces an inductive field within the copper laminae to warm the heating pile (which includes resin sheets (also known commonly as “pre-preg”)), and laminate the individual layers together. The solution created by this reference eliminates several of the detriments known in the related-art heating techniques for rapidly forming multilayer laminates, and has been widely adopted by the industry as a result. Unfortunately, the Ceraso process, while more rapid, fully fails to enhance accuracy and commonly incurs higher quality control loses that often costs more than the efficiency gained by the improvement in speed.
It is additionally recognized that multilayer rigid and flexible circuit boards (FSBs) can be manufactured by pin type registration systems to allow integration of a completed FSB into a complex geometry (e.g., a camera body). Typically, FSB's are joined by pins through conductive layers and (during layup) flexible portions project laterally from the plane of a rigid circuit board (in parallel thereto), such that the FSB portion (after processing) bends at an edge of a rigid circuit board. Examples of this construction are noted in Printed Circuits Handbook, 6th Edition, by Clyde F. Coombs, Jr., Chapt. 65, pages 65.1-65.10, the entire contents of which are incorporated by reference.
Unfortunately, the two above-noted conventional constructions have concerns with inherent errors, misalignment, and inefficiencies, particularly when using pin-type-layup procedures.
Applicant's related inventions in U.S. Pat. No. 8,051,121 issued Nov. 22, 2011, entitled Improved System for Manufacturing Laminated Circuit Boards, provide further improvements using computerized processor linked optical systems for corrective alignment for perfected stack orientation, and further eliminates the need for pin-type layups, and much more including the mechanical-operative systems for the same. The entire contents of U.S. Pat. No. 8,051,121 are fully incorporated herein by reference. Applicants other related inventions for further optical accuracy include U.S. Pat. No. 8,594,983 issued Nov. 26, 2013 and is also incorporated by reference.
Applicant's further related inventions in U.S. Ser. No. 12/377,268, entitled Bond Head Assembly and System, provides further improvements for automated and aligned electromagnetic bonding of PCBs. The entire contents of U.S. Ser. No. 12/377,268 are fully incorporated herein by references.
It will be understood that Applicant's related inventions involve an optical alignment system with processor control and an automated bonding system capable of bonding regions of panel layups as discussed in the respective references.
In combination, Applicant's above-noted inventions provide an enabling support for operative and automated optical alignment systems for manufacturing and bonding laminated circuit boards.
Referring now to FIG. 1, a conventional rigid-flexible board pin lay-up process 200 is discussed. As shown, a plurality of both outboard (around the periphery, as shown) and inboard (interior, as shown in two sets of four each) pins are shown at 201. Conventionally, these pins 201 create a number of detriments as will be discussed below. Opposing top and bottom lamination plates 202A, 202B must be custom made for each particular PCB and FSB constructed, even for a single use, and must be stored between uses. There between opposing top and bottom copper foil layers 203A, 203B are provided being also custom punched to align with pins 201. There between are also a prepreg bonding sheets 204A, 204B, rigid boards 205A, 205B, and film coverlays 207A, 207B. Interior of all of this is flexible circuit layer(s) 208. It will be understood that flex circuit layer 208 can include multiple flex circuit layers and is shown with a rigid outer portion. All arranged as shown in FIG. 1. The phrases prepreg, flex, and coverlay will be understood by those of skill in the conventional arts.
As a result, a conventional rigid-flex pin layup process 200, will at a minimum require the steps noted, including: (1) punching top and bottom lamination plates for all pin locations, (2) punching top and bottom foils at all pin locations, (3) punching top and bottom prepregs at all pin locations, (4) punching top and bottom rigid boards at all pin locations, (5) punching top and bottom film coverlays at all pin locations, and (6) punching the flex layer(s) which will require punching at all pin locations to enable all pins 201 to fully pass through the entire layup 200 for alignment. In this manner, the entire assembly 200 will be understood as a panel lay-up and includes the pins, lamination plates, and all components.
The conventional rigid-flex pin layup process 200 creates a number of detriments, well understood. These include, but are not limited to; (1) all holes must be punched or drilled on all materials individually without error, and this requires additional time as every layer must be punched or drilled accurately. Thus alignment of all hole-preparation is extremely critical on flex and rigid layer and results in substantial losses to quality control pre- and post-manufacturing.
Additionally, (2) lamination fixtures must be custom made, each specific to a particular job-circuit, and this requires that manufacturers both generate and then retain/store multiple custom lamination fixtures. Further, (3) When processing with outer layer foils, all holes must be placed prior to final lay ups—this requires additional time. Fourth (4) All prepreg layers must have additional clearance holes prepared for lamination pins prior to final lay-up. Fifth (5) All cover layers must have clearance holes or material cut-away from pining areas requiring additional planning, operations, and waste of time and materials. Sixth, (6) after a lamination cycle for a FSB, all pins must be manually knocked-out of the lamination book (the assembly itself) post interior-bonding in order to breakdown and remove the laminated rigid-flex board desired.
In summary, the current “state of the art” process requires pins placed near design features to locate the layers during the FSB assembly process (See FIG. 1). These pins also are used to minimize and control the movement of the various layers during the lamination press cycle where all the layers are laminated into a single structural unit. While this FSB process has been in use for many years and the use, particularly for rigid flex constructions is wide spread, it does have significant drawbacks that this invention addresses. These detriments include the existing process must be done by hand. It is not easily automated and has not been automated. The process is laborious and thus expensive. Each pin location must have a hole drilled, punched or lased (hole made with a laser) in each layer of rigid material, flex material, cover material, prepreg (a sheet of epoxy resin in the dry or “B” stage), bond ply, copper foil, separator plates and lamination plates. This is a considerable undertaking to accurately place holes in all of this material and often there are errors requiring loss of an entire PCB. Because the pins are in contact with the prepreg epoxy resin, bonding materials and adhesives, the pins are difficult to remove and can damage a PCB (printed circuit board) in the process of trying to remove the pins. The pins must be cleaned, in order to be reused. The pins are subject to wear and must be replaced. Worn pins can lead to layer to layer inaccuracies. The Applicant's invention described below removes these drawbacks and enables a PCB manufacturer to create rigid flex, flex and rigid printed circuit boards more efficiently. This new process will also allow automation to be utilized, if desired, to further improve manufacturing efficiency and/or layer to layer accuracy.
Therefore, the conventional arts provide substantial operational, and thus financial, detriments. Accordingly, there is a need for an improved system and method for manufacturing flexible laminated circuit boards (FSBs). Further, there is also a need to provide improved process efficiency when manufacturing flexible circuit boards (FSBs) that may be adapted to an optical or pin type lay up process.